Organ



April 3, 1934.

ORGAN Filed June 19, 1929 3 Sheets-Sheet 1 l, i. .l

FT@ T-x llg Humm a PMMA' N N C Db Eb E n F Gb G Ab A Bb E) Inventor April 3 1934. FQA. FIRE-STONE 1,953,753

ORGN

Filed June 19. 1929 5 Sheets-Sheet 3 Inventor fr! A. @M

Patented Apr. 3, 1934 'UNITED STATES PATENT ori-ica OBGAN Floyd A. FlrestonAnn Arbor, Mich. Application June 19, 1929, SerlalNo. 372,200

19 Claims.

The invention relates to an improvement in organs wherein the sound is produced by the generation of alternating currentsv of the proper frequency which currents are amplified and applied to a loud speaker. The objects of the improvements are to obtain an organ of greater tonal possibilities, more compact, and less expensive than the present compressed air organ.

The compressed air organ as usually built uses a separate set of pipes for each tone quality thus,

there is a full scale of pipes for imitating the clarinet tone, another for the trumpet, another for the flute, etc. A complete organ consists of about six thousand pipes together with the necessary equipment for supplying compressed air at different pressures. This equipment occupies a very large amount of space and costs $50,000 or more. Furthermore, its variety of tone qualities is limited by the inventiveners of the designers in producing pipes; many orchestral in- 4 struments have never been successfully imitated by the organ. My organ consists of one set of equipment which can by suitable manipulation imitate the tone of any musical instrument; it -ls less expensivel to construct than the compressed air organ and requires only as much space as a grand piano.

A musical tone consists of a fundamental tone and a number of harmonics. The pitch of the musical tone is determined by the number of vibrations per second, commonly called the frequency, constituting the fundamental tone. The harmonics have frequencies which are integral multiples ofthe fundamental frequency. Thus, if the fundamental frequency is 200 cycles per second, the second harmonic frequency will be 400, the third harmonic frequency 600l etc. The quality of a musical sound is that characteristic which enables us to distinguish the sound of the clarinet from 4that of the violin, or the piano frsm the banjo. The quality is determined by the intensity of the harmonics relative to the fundamental; by the rate at which the intensity of thefundamental and harmonics grows and decays at the beginning and end of a note, commonly called the attack; and by the accompanying noises such as the hiss of the violin bow or the clarinetists breath. My invention provides means by which the above three factors which will by the performer. It is at present held by many authorities that the phase of the harmonies relative tu the fundamental and to each other does not affect the tone quality but if the reverse should be found tobe true it is also posdetermine the tone quality may be controlled at sible for me to control the relative various component tones.

My device contains a separate alternating current generator for each fundamental and each harmonic of all the notes of the organ. These generators are controlled by the keys on the keyboard of the console. (The. console is that part of an organ which comprises the keyboards of the various manuals; the pedal keyboard, if any; and the necessary controls, if any, 'for regulating the loudness and tone quality of the notes produced). The currents are then amplified if necessary with a vacuum tube amplifier Awhose amphases of the plification is continuously variable for control-l ling the loudness; the amplified currents are applied to a loud speaker capable of converting electrical energy into acoustical energy.

Let us nowconsider what frequencies of alternating current must be produced in order to sound all of the Cs on the organ including their harmonics. There are on the organ 9 Cs having the following frequencies in cycles per second: l1'6, 32, 64, 128, 256, 512, 1024, 2048, and 4096. The lowest of these would` have a fundamental and harmonics of the following frequencies: 16, 32, 48, 64, 80, 96, 112, 128, 144, etc. Some of these harmonic frequencies are the same as the fundamental frequencies of the other Cs while some are different. The note havinga 32 cycle fundamental has frequencies of 32, 64, 96, 128, 160, etc. Some of theseA harmonic frequencies are the same as those in the previous list for the 16 cycle fundamental. Thus, when one considers the 9 Cs and, say, 20 harmonics of each, leaving out those harmonics having frequencies higher than 4096 cycles he finds that about different frequencies are required. For the C Sharps, 60 more different frequencies must be produced. Since there are twelve notes in one octave the production of all the notes in the scale with their first twenty harmonics, leaving out the harmonics above 10,000 cycles, would require '720 frequencies. It is obvious that if the device is to be commercially practicable each generator must be extremely simple.

Rossum Figs. 1a and 1b illustrate the principle of a single alternating current generator, which principle may be used in applying my invention. Figs.

2a, 2b,- and 2c show a practical combination of a inductor plug for each row of holes.

4 gives the wiring diagram of a typical portion of the complete organ.

For purposes of sound production no distinction need be made between alternating current and direct current with alternating current superposed. A simple alternating current generator capable of producing suiicient voltage to actuate the grid circuit of a vacuum tube can be produced in many different ways, but the method which I prefer is shown in principle in Fig. 1. A rotating ymetallic disc 1 on a shaft 2'is mounted in bearings 3 and 4 and driven by the synchronous motor 5 through the pulleys 6 and 7 and belt 8. Around the disc is a row of equally spaced holes 9. Two strips of metal 10 and 11 4called inductors are mounted on insulating blocks 12 and 13 in\such a manner thatthe holes 9 run close to them. If the switch 14 is closed von point 15 the battery 16 will charge the inductor -10. Owing `to the electrostatic capacity between inductor 10 and inductor 11 through the holes 9 the potential of the inductor 11 will always be greater when it is opposite a hole 9 than when it is opposite the grounded metallic disc 1 between .the holes 9. Thus an alternating potential will be developed on the inductor 11 having the frequency with which holes 9 pass the inductor 11. By properly shaping the inductor 11 and adjusting its distance from the holes 9 a pure wave free from harmonics can be obtained. The voltage thus generated may be taken to the conventional vacuum tube amplifier 17 which is connected to the loud speaker 18 through the potentiometer 19, The rate at which the generator builds up its voltage when the switch 14 is closed is governed by the resistance 21 and the condenser 22. The inductor 10 doesnot arrive at the full voltage of the battery until the battery has charged the condenser 22 through the resistance 21. It is well known that the time in seconds required to charge a condenser through 'a resistance is roughly equal to the Aproduct of the capacity in farads and the resistance in ohm's. Thus by adjusting the resistance 21 the generator may be made to build up its voltage instantly or gradually over a period of several seconds. To stop the generation of voltage it is necessary to discharge inductor 10. This is done through the resistances 23 and 21 by whose regulation the inductor 10 can be discharged instantly or gradually.A Experiment has shown that if the inductor 10 is charged to 200 volts the inductor 11 will deliver about'0.05 volts alternating current to the amplifier 17, a value ample for the operation of an amplifier.

The final form of generator group shown in Fig. 2 is arrived at by the expansion of the principle of Fig. 1 by the use of three discs on one shaft, eachl disc having many rows of holes and each row of holes having one inductor on each side of and close to the disc. For simplicity each disc in Fig. 2 is drawn withonly 6 rows of holes although in practice a larger number is required as explained fully further on in this.l paragraph. 24, 25, and26 are the three metallic discs which are xed to the shaft 27. Shaft 27' is mounted in the bearings 28 and 29 and is driven by belt 30, 31, 32, and 33 are the insulated primary inductor groups to which the direct polarizingr voltage is applied, there being a separate insulated metallic 34, 35, and 36 are the .corresponding insulated secondary inductor'grups from which the alternating currents are derived, there being a separate insulated metallic inductor plug for each row of holes. Arranged in any convenient manner on discs 24,

25, and 26 are concentric circular rows of holes,

there being one each of rows having the following numbers of holes: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,

176, 192, 208, 224, 240, 256, 272, 288, 304, and 320. The purpose of using three discs 24, 25, and 26`is merely to have sufficient room for so many rows of holes. The rows which vgenerate the fundamental frequencies in the above group have the following numbers of holes: 1, 2, 4, 8, 16, 32, 64, 128, and 256. Theprest ofthe rows are necessary for providing the 20 harmonics of eacn of these fundamentals, all rows having more than 320 holes having been omitted' as being of too high a frequency.

If the generator group of Fig. 2 is driven at 16.00 revolutions per second it is capable of producing all the frequencies necessary for all the Cs of the scale and all their necessary harmonics. An exactly similar generator group if driven at va speed of 16.95 revolutions per second is capable of producing all the frequencies necessary for all the C Sharps of the scale and all their neceary harmonics. The frequencies of all the notes .of the musical scale. and'all their necessary harmonies can be produced by 12 similar generator groups running at the following speeds in revolutions per second: 16.00, 16.95, 17.96, 19.02, 20.15, 21.35, 22.62, 23.97, 25.39, 26.90, 28.50, and 30.19. The foregoing numbers are in the relation of the frequencies of the equitempered scale each being larger than the one just preceding by the twelfth root of 2.- l

Fig. 3 shows schematically the entire generator assembly. 'The synchronous motor 37 drives the line shaft 38 through the belt 39. This line shaft drives the twelve generator groups 40 through the belts 41 each pulley 42 being of such size as to drive its generator group at one of the speeds listed above. In operation the metal parts of all generators are grounded.

Fig. 4 shows a )schematic diagram of the manner in which the generators are connected into the circuit so as' to allow the musician to control them from the keyboard. 43 is the lowest C key on the keyboard; 44 is the next higher C key and 45 the next higher C above 44. These keys are provided with a multiplicity of contacts 46 arranged as shown so that when the key is depressed the primary 'inductors of the generators 47 are connected to the polarizing battery 48 through the voltagev selecting switches 49 and the variable resistors 50; but when the keys are released the primary inductors of generators 47 are connected to ground through the variable resistors 47 and 51. The contacts on each key of course connect with those generators with frequencies appropriate to the fundamental and harmonics of that particular no'te in the scale. The symbol which has been chosen to represent these electrostatic generators in the diagram is that for a condenserwith a numeral in the center whichin'dicates the number of holes in the row of that particular generator. It will be noted from the drawings that the 1 hole generator is controlled by the fundamental contact that if either key is depressed the primary inductor of the generator is disconnected from the grounding resistor 51 and connected tothe y, has been said to indicatethe manner in which Aso the C -keys are connected with the C `group of generators. The C sharp keys and the C sharp group of generators form a' set of connections separate from the C keys except that the C sharp groupderives lits polarizing voltage from the' same switches 49 and the secondary inductors of the C sharp generator group are also connected to the input grid of the amplifler 17. Similarly for the other notes of the scale. 'Ihe secondary inductors of all the generators are permanently connected to the input grid of the amplifier 17 and thence through the potentiometer 19 to the loud speaker 18, but alternating voltage is supplied only by those generators whose primary inductors are charged. If the generators are built for 20 harmonics of each note then there will be 20 sets of contacts 46 on each key except those near the top of the scale, and 20l sets of resistors 47 and 51 and condensers 52-for each key except 'those near the top of the scale. There are, however, only 20 switches 49 for each manual of the organ as one switch regulates the voltage for all the fundamentalvfrequencies, another switch regulates the voltage for all the second harmonic' frequencies, etc. :By setting the switches 47 the musician has absolute conta-ol of the steadyi state tone quality of the notes produced by the loud speaker 18. 'Ihe different manuals of the organ use the same set ofgenerators but each manual has a separate set of switches 49 for controlling the relative intensity of the harmonics. Thus while the lowest 'note played on one manual might consist mainly of fundamental, this same pitch played on another manual might be very richin harmonics. y

' The purpose of condensers 52 in conjunction withv resistors 50 and 51 is to regulatethe attack on the notes as was previouslyL pointed out in the explanationof Fig. -1.` 4

It is obvious from the connections of Fig. 4 that if two keys are simultaneously depressed two voltages may at the same time be applied to one of the 'primary inductors of a generator 47. In such a case it is desirable that the resultant voltage should be approximately equal to the largest of the two. 'Ihis result is achieved by placing resistors 53 in -series with the voltage vsulivli? leads, the resistance in the higher voltage leads being less than the resistance in thek lower voltage leads. a

InV the above description of the -method of connecting the generators it has been assumed that there is only one generator of each of the ductm. :night be disposed tangenuniiy along s single row of, holes and thus serve as several separate generators of the 'same frequency with-- out an-increase in the number'of discs required. In some cases this 4might be of advantage in simplifying the connections as each harmonic would have its own generator and nog'enerator be suitable. Its construction must be such as to toserve more than one purwould be' required pose.

If it should be found that the relative phase of the various harmonics iniiuences thetone quality, then each pair of inductors on the generatorsmay be arranged to move a short distance tangentially from its normal position and in this way the relative phases of the generated currents can be varied. 'i

The electrostatic generators as described above can be constructed in many forms which will in the disc pass. Or with thisconstruction the` of regulating the attack, in the simple circuit of Fig. 1 the rate of growth and decay of charge on inductor 10 are regulated merely `by resistance 21 and condenser 22. These two circuit elements may however be replaced by a more complicated series parallel arrangement ofresistances, condensers and inductances, .thereby securing a more complicated form of attack and decay, the exact form of circuit chosen depending on the judgment of musical taste on listening to the notesA produced. The amplifier may utilize as many stages as necessary and be of sufficient power to supply the necessary volume without harmful distortion. The loud speaker may be any sort `of suitable device for converting electrical energy into acoustical energy although it is preferable that it should have a minimum amount of resonance so that the response may be quick and free from frequency distortion. A good cone speaker, horn speaker, or Hewlett tone generator would4 allow it to handle the comparatively large energy. What I claim is: 1. -In combination, means of generat'ng alternating currents of a` multiplicity of frequencies, a loud speaker, and means for regulating as a function of the timetheamount of current of any frequency supplied by said generating means loud speaker, and means for regulating the rate of' starting of the aforesaid delivery of alternating current.

a. In combination, s munfpncity of alternating current generators, a loud speaker, means for Starting and stopping the delivery of alternating current from anyV aforesaid lgenerator to said loud speaker, means for regulating the rate of starting of the aforesaid delivery of alternating current, and means for regulating the rate ofvl fi. In combination, means of generating alternating currents of a multiplicity of frequencies,

a loud speaker, and means for regulating as a function of the time the amount of current of any frequency supplied from said generating means to said loud speaker.

5. In combination, means of generating alternating currents of a multiplicity of frequencies, means for regulating as a function of the time the amount generated of alternating current `of each frequency, an amplifier, and a loud speaker.

6. In combination, means of generating alternating currents having the frequencies of the notes of the musical scale and their harmonics, means for regulating as a function of the time the amount generated of alternating current of each frequency, an amplifier, and a loud speaker.

7. In combination, a multiplicity of alternating current generators, means for amplifying alternating currents, means forstarting and stopping the delivery of alternating current from any aforesaid generator to said amplifier, means for regulating the rate of startingy andthe rate of stopping of the aforesaid delivery of alternating current, and means for producing sounds from the amplified alternating currents. I

8. In combination, a. multiplicity of alternating current generators, generating the frequencies of the notes of the musical scale and their harmonics, means for amplifying the alternating currents generated by said generators, means for starting and stopping the delivery of alternating,

current from each aforesaid generator to said amplifier, means for regulating the rate of starting and the rate of stopping of the aforesaid delivery of alternating current, and a means for producing sounds from the amplified alternating currents.

9. In combination, a multiplicity of alternating current generators, a console, means for amplifying alternating currents, means controllable from said console for reguiating as a function of the time the amount of alternating current delivered from any aforesaid generator to said amplifier, and means for producing sounds from the amplified alternating currents.

10. In combination, a multiplicity of alternating current generators generating the frequencies of the notes of the musical scale and their harmonics, a console, means for amplifying alternating currents, means controllable from said console for regulating as a function of the timel the amount of' alternating current delivered from any aforesaid generator to said amplier, and means for producing sounds from the amplified alternating currents.

11. In combination, a multiplicity of electrostatic alternating current generators each of which comprises a moving member, a primary inductor, and a secondary inductor, the mutual electrostatic capacity between said primary and secondary inductors -being periodically varied by said moving member; a console having several manuals of keys; separate means for each manual for controlling the charge on the primary inductor of any generator as a function of the time; means for amplifying the alternating currents produced by said generators; and means for producing sounds from the'amplified currents.

12. In combination, a multiplicity of electrostatic alternating current generators each of whichjcomprises a moving member, a primary inductor, and a secondary inductor, the mutual electrostatic capacity between Vsaid primary andv secondary inductors being varied periodically by said moving member; means for controlling'the charge on the primary inductor of any generator as a function of the time; means for amplifying the alternating currents produced by said generators; and means for producing sounds from the amplified currents.

13. In combination, a multiplicity of electrostatic alternating current generators each ofv which comprises a moving member, ar primary inductor, and a secondary inductor, the mutual electrostatic capacity between said primary and` which comprises a moving member, a primary inductor, and a secondaryinductor, the mutual electrostatic capacity between said primary and secondary inductors being varied periodically by said moving member; a console; means operable from said console for controlling the charge on any of the primary inductors of said generators; means for amplifying the alternating currents generated by said generators; means for producing sounds from the amplified alternating currents; and means `for controlling the amount of alternating current delivered by said amplifier to said sound producing means.

15. In combination, a multiplicity of electrostatic alternating current generators each of which comprises an insulated primary conduct ing plate, an insulated secondary conducting plate, and a moving member so shaped and so placed as to periodically vary the mutual electrostatic capacity between said primary and secondary conducting plates; means for controlling the charge on the primary conducting plate of any generator as a function of the time; and means for producing sounds from the voltages induced on the secondary conducting plates.

16. In combination, 'a multiplicity of electrostatic alternating current Agenerators each of which comprises an insulated primary conducting plate, an insulated secondary-conducting plate, and means for periodically varying the mutual electrostatic capacity between said primary and secondary conducting plates; means for controlling the charge on the primary conducting plate of any generator as a function of the time; and means for producing sounds from the voltages induced on the secondary conducting plates.

17. In combination, a multiplicity of electrol static alternating, current generators each of which comprises an insulated primary conducting plate, an insulated secondary conducting plate, and means for periodically varying the mutual electrostatic capacity `between said primary and secondary conducting plates; means for charging the primary conducting plate of any generator;

' 'means for utilizing part of the 'electrical energy induced on the secondary conducting plates.

18, In combination, an electrostatic alternating current generator comprising conducting members insulated from each other, means for periodically varying the mutual electrostatic cafor periodically varying the mutual electrostatic I capacity between said conducting members, means for controlling the charge on some aforementioned conducting members as a function of the time, an ampliler, and a loud speaker.

FLOYD A. FIREBTONE. 

